ext4: drop fast_commit from /proc/mounts

The options in /proc/mounts must be valid mount options --- and
fast_commit is not a mount option.  Otherwise, command sequences like
this will fail:

    # mount /dev/vdc /vdc
    # mkdir -p /vdc/phoronix_test_suite /pts
    # mount --bind /vdc/phoronix_test_suite /pts
    # mount -o remount,nodioread_nolock /pts
    mount: /pts: mount point not mounted or bad option.

And in the system logs, you'll find:

    EXT4-fs (vdc): Unrecognized mount option "fast_commit" or missing value

Fixes: 995a3ed6 ("ext4: add fast_commit feature and handling for extended mount options")
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -2638,10 +2638,6 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
 	} else if (test_opt2(sb, DAX_INODE)) {
 		SEQ_OPTS_PUTS("dax=inode");
 	}
-
-	if (test_opt2(sb, JOURNAL_FAST_COMMIT))
-		SEQ_OPTS_PUTS("fast_commit");
-
 	ext4_show_quota_options(seq, sb);
 	return 0;
 }